1. Technical Field
This invention relates to a method and apparatus for covering an object with a sheet of flexible material and, more particularly, to an assist fixture in combination with a fluidized bed for bonding a cover material to a contoured substrate such as a urethane pad to form an attractive assembly retaining soft-surface touch as well as providing sharp definition of features.
2. Background Art
Numerous commercial products are formed by adhering a fabric cover or other such material to rigid and semi-rigid foam panels. Adhering the sheet material to a nonplanar substrate is quite difficult especially when it is required that the adhered fabric have the same profile or contour as the nonplanar substrate. One good example of such a product is the seat or the interior door panel incorporated into a vehicle such as an automobile.
Typically, these vehicle panels are required to include decorative features and simulate the pleats that would be associated with a traditional cut-and-sew assembly. It is generally desired that all the contour features be comfortable to the touch and appealing to the eye, for which reasons each contour feature is generally covered by a layer of fabric or other suitable sheet material, such as vinyl or leather, that may include bilaminate or trilaminate constructions. Methods of constructing such an assembly in an economical manner, which reduce costs or eliminate labor-intensive steps, are always being sought.
An exemplary fabrication is disclosed in U.S. Pat. No. 4,692,199 to Kozlowski wherein high temperature steam is forced through a porous mold to heat and diffuse an adhesive film into adherence with an adjacent fabric layer and foam pad to secure the two together. However, high temperature steam can be detrimental to the foam and require additional overbuild of the foam to compensate for height loss. Accordingly, this translates into a more costly product.
By using hot air instead of high temperature steam, such as with a fluidized bed, there is no detrimental result to the foam. In the process for covering an object such as a seat disclosed in application Serial Number WO 90/00519, published Jan. 25, 1990, a fluidized bed of particles is covered with a porous pliable membrane, a flexible cover is placed above the membrane, pressure is applied to the object, the flexible cover is deformed as the object is immersed in the fluidized bed until a mating imprint is formed on the object. The covering can be effected by gluing, in particular with a previously applied heat-activated adhesive, in which case the fluidized bed is obtained by means of a current of hot air at a temperature above the activation temperature of the adhesive.
The fluidized bed approach is attractive, particularly when compared to other bonding processes, because no costly custom-designed molds are required for the bonding setup. Further, as the complexity of the contour increases, so will the registration of the cover to the foam, the amount of sharp definition attainable without bridging of the cover sheet, and the possibility of wrinkles in the cover sheet.
Accordingly, it is an object of this invention to provide a novel method and apparatus for constructing a vehicle seat or trim panel of foam and having a soft surface touch.
A further object of this invention is the elimination of labor-intensive steps in bonding fabric to a foam pad.
Another object of this invention is provision of an economical method of bonding a seat cover to a foam pad wherein the seat cover can be attached to a frame before the bonding process so that the seat is complete when removed from the press.
Another object of this invention is the provision of a novel assist fixture to provide definition on the appearance surface of the cover sheet subsequent to the bonding process.
A further object of this invention is provision of an assist fixture in which hot and/or cold air can be circulated to shorten the cycle time of the bonding process.